A method for adjusting a fuel injector, as well as a fuel injector are described in German Published Patent Application No. 40 23 828. To adjust the flow quantity of a medium released during the opening and closing process of an electromagnetically actuable fuel injector, a magnetically conductive material is introduced into a blind-end bore, in powder form, for instance, the material being able to change the magnetic properties of the inner pole, thereby varying the magnetic force, until the measured actual flow rate of the medium corresponds to the predefined setpoint quantity.
It is described in German Published Patent Application No. 40 23 826 to insert an adjusting bolt into a blind-end bore of an inner pole provided with an opening at its periphery, and thereby vary the magnetic force. The adjusting bolt is inserted such that the measured actual quantity conforms to the predefined setpoint quantity.
In German Published Patent Application No. 195 16 513, a method is described for adjusting the flow rate of a dynamic medium of a fuel injector. In this case, an adjusting element positioned near the magnetic coil, outside the flow route of the medium, is adjusted, causing a change in the magnitude of the magnetic flow in the magnetic circuit and, thus, in the magnetic force, so that the flow rate of the medium is able to be influenced and adjusted. The adjustment may be performed both in a wet and a dry fuel injector.
German Published Patent Application No. 42 11 723 describes a fuel injector and a method for adjusting the flow rate of a dynamic medium of a fuel injector. In this case, an adjustment sleeve, having a longitudinal slit, is pressed into a longitudinal bore of a connecting piece up to a predefined pressing depth, the valve's instantaneous quantity of a dynamic medium is measured and compared to a setpoint quantity of the medium, and the pressed-in adjustment sleeve, which is under a tension acting in the radial direction, is advanced until the measured instantaneous quantity of the medium conforms to the predefined setpoint quantity of the medium.
As described in German Published Patent Application No. 44 31 128, to adjust the flow rate of a dynamic medium of a fuel injector, a deformation of the valve housing occurs by a deformation tool engaging on the outer circumference of the valve housing. In the process, the size of the residual-air gap between the core and the armature and, thus, the magnitude of the magnetic force, changes, so that the flow rate of the medium is able to be influenced and adjusted.
Particularly disadvantageous in the group of methods, which influence the magnitude of the magnetic flow in the magnetic circuit, is the high production cost, since the required static flow-rate tolerances must be assured, which is difficult to realize, however. The measurements of the magnetic fields are costly and, in most cases, require cost-intensive methods and also a testing field.
Disadvantageous in the group of mechanical adjustment methods, in particular, is the high imprecision to which these methods are subject. Furthermore, the opening and closing times of a fuel injector can only be shortened at the expense of the electric output, thereby increasing the electrical load of the components and placing greater demands on the control devices.
Especially the method described in German Published Patent Application No. 44 31 128, in which the residual-air gap between the core and armature is modified by deformation of the valve housing, is unable to correct the flow rate with high precision, since shear stresses in the nozzle body influence the direction and magnitude of the deforming force in a disadvantageous manner. For this reason, all parts require high manufacturing precision.